Yeast Artificial Chromosomes (YACs) permit the cloning of 0.2 – 2.0 Megabases. YACs are propagated in yeast as a linear chromosome which becomes part of the genome and is distributed by the mitotic machinery. YACs must include:
- centromere sequences (CEN)
- Telomere sequences (TEL)
- Autonomous replicating sequences (ARS) for replication in the yeast nucleus.
- Ampicillin resistance for propagation in E. coli
- Three markers including a suppressor tRNA gene, TRP1, and URA3 genes for selection by complementation in the appropriate yeast host cell.
5. Cloning systems for producing mutagenized DNA:
Cell-based oligonucleotide mismatch mutagenesis can be used to generate a specific nucleotide substitution in a coding sequence of a gene. This is achieved by using M13 vectors to generate single-stranded recombinant DNA 
Production of single-stranded DNA for use in sequencing is obtained using M13 vectors or phagemid vectors. 
PCR-based mutagenesis could be used to achieve two types of changes:
- 5’ adds-on mutagenesis which adds specific sequences at the 5’ of the amplified product. Such sequences may include a phage promoter to drive gene expression.
- Site-directed mutagenesis which results in an amplified product with a specific base substitution to introduce a specific amino acid substitution at the protein level. 
